Fix a11y violation in Notification/Global Storybook (#6429)
Fix a11y violation in Notification/Global Storybook (#6429)

* Fix a11y violation in Notification/Global sb

* Keep both Headers and add Main

Co-authored-by: Eric Soderberg <7357255ec89aa29cb38b14d4ed1295aca420bf0b@hpe.com>
grommet/grommet,grommet/grommet,grommet/grommet